This invention relates to lubricants and, more particularly, to food grade lubricating oils which are especially useful as compressor or vacuum pump oils for equipment utilized in the food service industry.
The equipment used in the food processing industry varies by segment with the three leading segments being meat and poultry, beverages, and dairy. While the equipment varies from segment to segment, the majority of manufacturing operations require significant amounts of compressed air. Due to the importance of ensuring and maintaining safeguards and standards of quality for food products, the food industry must comply with the rules and regulations set forth by the United States Department of Agriculture (USDA), originally under The Food Safety and Inspection Service (FSIS), as part of the Federal Food, Drug and Cosmetic Act (FFDCA), which holds responsibility for all programs for the inspection, grading, and standardization of meat, poultry, eggs, dairy products, fruits, and vegetables.
Under the FFDCA, specifically section 21 CFR 178.3570, lubricants which are susceptible to incidental food contact are considered indirect food additives under USDA regulations. Lubricants classified as “H1” are authorized for incidental food contact. H1 authorized lubricating oil and the term “food grade” will be used interchangeably herein and in the appended claims.
Several market factors accentuate the need for a superior food grade lubricating oil. Some manufacturers prefer to use only H1 authorized oils to avoid the possibility of noncompliance. Reducing contamination risks and inventory carrying costs associated with stocking multiple inventories of varying viscosity/FDA approval level oils also provides an economic incentive for exclusive use of H1 authorized oils. Furthermore, other firms, reliant upon company image as a marketing resource, may elect to take the conservative approach to health and safety issues and utilize only H1 authorized oils. All of these concerns are addressed by the exclusive use of H1 authorized oils.
In addition to meeting the requirements for safety set by federal regulatory agencies, the product must be an effective lubricant. Lubricating oils for food processing plants should lubricate machine parts, resist viscosity change, resist oxidation, protect against rusting and corrosion, provide wear protection, prevent foaming, and resist the formation of sludge in service. The product should also perform effectively at various lubrication regimes ranging from hydrodynamic thick film regimes to boundary thin film regimes.
The oxidation, thermal, and hydrolytic stability characteristics of lubricating oil help predict how effectively an oil will maintain its lubricating properties over time and resist sludge formation. Hydrocarbon oils are partially oxidized when contacted with oxygen at elevated temperatures for prolonged periods of time. The oxidation process produces acidic bodies within the lubricating oil which are corrosive to metals often present in food processing equipment. Many metals present in food processing equipment and in contact with both the oil and the air are effective oxidation catalysts which further increase the rate of oxidation. Oxidation products contribute to the formation of sludge which can clog valves, plug filters, and result in the overall breakdown of the viscosity characteristics of the lubricant. Under some circumstances, sludge formation can result in plugging, complete loss of oil system flow, and failure or damage to machinery.
The thermal and hydrolytic stability characteristics of lubricating oil reflect primarily on the stability of the lubricating oil additive package. The stability criteria monitor sludge formation, viscosity change, acidity change, and the corrosion tendencies of the oil. Hydrolytic stability assesses these characteristics in the presence of water. Inferior stability characteristics result in the lubricating oil losing lubricating properties over time and precipitating sludge.